The present invention generally relates to an industrial articulated robot, and more particularly relates to a structure of an articulated portion of rotatable arms.
Generally, in an articulated robot of this kind, a plurality of arms are rotatably supported in a linked manner on a base portion as a means for transmitting a driving force. The the driving sources are disposed separately from the base portion of the robot. When the arms perform their turning movements, the motors become loads for the rotational movements causing great inertia force. Therefore it is difficult to accurately position the robot arms additionally, in order to prevent the robot from falling down forward, sufficient stiffness is required for the attaching portion of the base portion of the robot.
For example, Japanese Patent Unexamined Publication No. 7593/84 discloses an arrangement in which an arm driving motor is fixed on a base and the rotation of the motor is transmitted to articulated portions through transmission means constituted by, a belt and pulleys. Harmonic decelerators are incorporated in the respective articulated portions so as to decelerate rotation of the motor resulting in a deceleration of the arms.
The articulated portions of the arms are supported in a state of a cantilever, so that the attitude of the arms becomes unstable during deceleration. Therefore, the arms have a tendency to fall in the forward direction. In addition, it becomes difficult to attach rotary position sensors due to the manner in which the arms are connected. Further, since the driving motor is attached to the fixed base, the rotation transmission mechanism becomes complex thereby making it difficult to attach other driving source, such as a driving motor for a work shaft provided at the forward end of the arm, onto a portion of the fixed base.